Working with students for 15 years has taught awarding-winning high school teacher Ed Galindo that toilet humour is a sure-fire way of getting attention.

Thus was born "Fun With Urine," the wackiest of more than 80 experiments on the space shuttle Columbia's 16-day science mission.

The experiment, sponsored by Native American students from the Shoshone-Bannock Indian Reservation in rural Idaho, tackles a serious problem for the future of human space flight: how to combat depression in long-term space voyagers, Galindo said.

The solution the students are testing on Columbia is art therapy and, more particularly, painting with urine-based paints.

"To get the students' attention, you have to get them out of their comfort zone sometimes," said Galindo, Idaho's Science Teacher of the Year.

Urine was chosen as a component of the paint because it is naturally recurring resource that would allow for an endless supply of paint for a trip, say, to Mars. For colour, the students learned from tribal elders about pigments from berries and plants, all approved by NASA for space flight.

Students interviewed psychologists about potential for depression on long space flights, studied the experiences of submariners and astronauts and learned the physics of paint and the chemistry of urine.

"It isn't just a science class where you learn just about one science topic. We look at things more holistically, where art is related to science and chemistry is related to art," said Galindo.

Students painted various objects with the urine-based paint and the shuttle's astronauts are monitoring them to see if the paint degrades in space.

Like all experiments, this one has had to overcome its share of unforeseen glitches. The first occurred when word spread on the reservation about the experiment and unsolicited urine donations began pouring in.

"I had all these people wanting to donate and I had almost 114 litres in my lab," Galindo said. "I think they just wanted their urine up in space and they thought it was the thing to do."